The present invention relates to femoral neck osteotomy, and more particularly to an osteotomy guide assembly and method for cutting a femoral neck at a desired angle in relation to the long shaft of the femur.
The femur 2 (See FIG. 5) articulates with the acetabulum by a rounded head 6 connected with the shaft 9 of the bone by an oblique neck 7. A pair of eminences called trochanters are located at the junction of the neck and shaft for attachment of muscle. The greater trochanter 4 is situated at the outer part of the upper (or proximal) end of the shaft at its junction with the neck, and the lesser trochanter 5 is at the lower back part of the junction of the shaft and neck. The upper portion of the neck between the greater trochanter and the head is referred to as the saddle portion 8.
Hip arthroplasty typically requires cutting off the head and neck of the femur (such as along line "L" indicated in FIG. 5). The precision of this cut is important to the proper placement of the hip prosthesis implant which will subsequently be installed into the femur. Various types of osteotomy or cutting guides have been utilized for cutting off the head and neck of the femur.
U.S. Pat. No. 4,621,630 to Kenna discloses a guide for femoral neck osteotomy comprising a longitudinal rod having attaching structure at the lower end thereof for securing the rod to a femur at the greater trochanter. A transversely extending support arm is secured to the rod adjacent the lower end thereof, and a guide bar is connected to the support arm. The guide bar has at least one elongate planar surface disposed at an angle to the axis of the rod. A cutting instrument is used in engagement with the planar surface to guide the cutting instrument in cutting the femoral bone at the desired angle. The guide bar is slideable along the support arm toward or away from the longitudinal rod for transverse positional adjustment, but is prevented from rotating relative to the support arm. U.S. Design Pat. No. 282,277 to Kenna also illustrates the ornamental features for a guide for femoral neck osteotomy which corresponds to the guide shown in U.S. Pat. No. 4,621,630.
A Femoral Neck Resection Guide, illustrated in literature for Osteonics Corp., discloses a guide assembly which fits over a reamer shaft which has been used to ream the medullary canal. The assembly includes a block having a hole therethrough for fitting over the portion of the reamer shaft extending from the femur. A resection cutting or saw guide having an angled cutting surface is aligned so that the cutting surface is parallel to the intended cutting plane on the bone. This is done by adjusting the axial position of the guide in relation to the elongated reamer shaft. The guide is anchored to the shaft in the desired position by tightening a locking screw. The cut in the bone is made up to the approximate depth of the intramedullary reamer. The reamer and guide assembly are removed and the resection of the neck is completed.
A Femoral Neck Cutting Guide is illustrated in literature for Howmedica, Inc. for the PCA Hip. The cutting guide is secured to the greater trochanter by impacting pins protruding from an elongated shaft into the bone of the greater trochanter. A transverse bar extends from the shaft. A cutting bar is attached to the shaft. Two different locking mechanisms are utilized to locate the position of the cutting bar to the transverse bar. One locking screw adjusts the transverse position of the cutting bar along the transverse bar. A second separate locking mechanism adjusts the axial position of the cutting bar in relation to the transverse bar, and thus axially along the longitudinal direction of the femur.
A Surgical Technique, by Gustilo and Kyle, for the BIAS Total Hip System (.COPYRGT.1986 Hennepin County Medical Center), discloses an osteotomy guide which has a barrel with a fixed transverse bar extending therefrom and a fixed cutting guide attached thereto. The barrel fits over the protruding end of an intramedullary reamer. The cutting guide has a flat shape which corresponds to an anterior-posterior view of the neck portion of a hip prosthesis implant with a cutting slot partially extending into the medial side of the plate. A plurality of holes is provided on the neck portion to aid in alignment for hip stem prostheses of varying neck lengths. Clear acrylic templates with an outline of the stem to be implanted may be used in conjunction with the osteotomy guide to aid in positioning of the guide. This guide does not provide for adjustment of the cutting guide plate relative to the transverse bar since it is in a fixed relation thereto.
The Surgical Technique for the Harris Precoat Hip Prosthesis (.COPYRGT.1984 Zimmer, Inc.) discloses a neck osteotomy guide that is a flat piece of metal cut in the outline of a flag and depending stem. It includes positioning cutouts or holes to aid in alignment for hip stem prostheses of varying neck lengths. The guide is superimposed over the femoral shaft with the posterior surface of the flag abutting the femoral head and with its stem in line with the midline of the medullary canal. The inferior margin of the flag portion of the neck osteotomy guide indicates the position for the osteotomy. This guide is not physically attached to the femur.
The Surgical Technique for the Harris/Galante Porous Hip Prosthesis (.COPYRGT.1984 Zimmer, Inc.) discloses a neck osteotomy guide that is a flat piece of metal cut in a shape corresponding to the anterior-posterior view the hip prosthesis stem to be implanted, having a neck and depending stem portion. A cutting slot is provided between the neck and stem portion which partially extends into the medial side of the plate. The neck and depending stem portion are connected along the lateral side of the plate. A reference scale is provided along the medial side of the plate. The plate is superimposed on top of the femur and is not physically attached to the femur. Clear acrylic templates with an outline of the stem to be implanted may be used in conjunction with the osteotomy guide to aid in positioning of the guide. The templates are typically superimposed over a patient's X ray during preoperative planning. The template also includes a medial scale which can be used to reference positioning with the corresponding scale on the osteotomy guide during surgery.